Ultrahigh frequency oscillator



ug. 9, 1938. A H, TURNER 2,125,969

ULTRAHIGH FREQUENCY OSC ILLATOR Filed Aug. 29, 1935 Q y M@ 45 cathode lead I1. A suitable radio frequency tallic shield at points adjacent the axial poles. 45

PatntcdAug. 9, 193s UNITED STATES PATENT .o1-FICE ULTBAHIGH FREQUENCY OSCILLATOR Alfred Turner, Collingswood, N. J., assignor to Radio Corporation of America, a corporation of Delaware Application August 29,1935, serial No. 38,314 i` claims. (ci. 25o-sc)- My invention relates to oscillators. More parnection with the metal tubes. but also form a ticularly, my invention is an ultra high frequency tight mechanical t to hold the adjusted tubes transmitter in which the oscillatorv proper is at .the proper position and keep out moisture. contained within a small Vshielded metal con- The grid leak, cathode and one of the heater 5 tainer which may be positioned intermediate the leads 3| may be connected'together and to the ends of an antenna. metallic shield at a p oint remote from the axial `One of the objects of my invention is to enclose sockets. 'I'he other heater lead and choke lead themionic tube within a metallic shieldwhioh is are insulated and brought out. through suitable part of the-tank circuit of the tube. l holes inthe shield. These leads are vconnected Another object is to enclose an oscillator within to a power source 33, such as a battery, motorl0 a metallic shield which may be included in the generator, or the like. The power source 33 may antenna system of an ultraA highv frequency be remote from the shield, and may be at ground transmitter. potential with respect to radio frequency A still further object is to combine the oscillacurrents. tor, shield and antenna of an ultra high fre- The arrangement described maybe operated as 15 quency system. an ultra high frequency oscillator, or a receiving Further objects will appear in the accompanydevice.- The tuned or resonant tank circuit coning specification and claims. i sists of the inductance of the copper shield mem- Figure I is a view, partly in section, of one ber and the variable capacity composed of the embodiment of my invention, l Vslidable armatures 3 5. The variable capacity 20 Figure II is a view, partly in section, of a modiis coupled through the metal bands 'I-9 to the cation of Figure I, grid and anode electrodes. ',The circuit ar- Figure III is an illustration, partly in section, rangement of Figure I is that vof a single tube of a push-pull ultra high frequency oscillator Hartley oscillator. 4 r, l5 adapted to my invention, f By way of example, the shield may be made of 25 Figure IV is an illustration, partly in section, a pair of copper cans, about two inches in diamof a modified form of push pull device, and eter and four inches long.V The copper tubes Figure V is adiagram showing an embodiment may be made of rods of outside diameter.l of my invention which is suitable for frequency The glass tube may be made of Pyrex vor other control. suitable insulation. The walls of the glass tube 30 In Figure I within a suitable glass tube I are may be about 515'/ thick. The copper bands are slidably mounted two metal tubes 3-f-5. These about 1A" wide.' With valuesof the order given, tubes are preferably good conductors, such as stable oscillations may be generated from 400 to copper, closed at their inner ends.- They form 600 mgacycles. w .15 the two armatures of an adjustable condenser. y 'I'he arrangement I have described maybe 35 Two metallic bands, 1 9, of copper or like concombined with a4 direct radiating antenna s'ysi ductor, are mounted on the outside of the glass tem.` 'Ihe radiating antenna conductors :i5- 31 tube.` The two bands are insulated from each may be connected directly to the metallic shield other. `One of the bands 1-is connected, preferbecausepat the high `freuuencices employed the 40 ably directly, to the grid lead II of a thermionic shield has a suitable impedance for a direct an- 40 tube, such as an RCA type 955. The other band tenna connection. Each of the `antenna con- 9 is` connected to the plate lead I 3 of the same ductors 35-31 are preferably a. quarter wave tube. The grid isl connected through a grid leak length long. At the lower'y frequencies the anresistor I5 of the order of 50,000 .ohms to the tenna conductors may be connected to the mechoke I9 is mounted adjacent the plate lead I3 At higher frequencies a betterimpedance match and is connected thereto. will be foundat a pair of points nearer the equa- Ahollow metallic shield 2|, which may be fabtorial region of the shield. The antenna. conricated from. two hollow copper hemispheres ductors may be wires oi'4 tubes of suitable cross 23-'25 or the like. surrounds the adjustable conj section. They may be iixed to the shield by soi- 50 denser and tube. The shield is made with indering, brazing, or the like. Wardly turned sockets21--29 adjacent the axial The construction is designed to makeA a-weathpoles. rlfhe sockets make good spring contacts erproof unit. Afterthe frequencyhas been adwith the slidable armatures of the condenser. justed by positioning the armatures, they maybe The sockets not ronly make good electrical consoldered or sealed to the shield to make the as- 55 sembly weatherproof. The unit may be supported or self supporting. It may be used with or without a reflector. The antenna wires may be vertical or horizontal. It is especially adaptable to aircraft or other mobile units.

Figure II illustrates an embodiment of my invention not unlike the arrangement shown in Figure I. 'I'he essential differences in the two' arrangements will be found in the substitution of a cylindrical shield 4| for the spherical shield Apositioned a pair of metallic bands 51-59. One

of the bands 51 is connected to the grid lead 6| of the thermionic tube 63. The other metallic band 59 is connected to the grid lead 65 of the other thermionic tube 61. These thermionic tubes may be of the small acorn type known as RCA 955. The plate leads 69 of these two tubes are connected together. 'I'he center point 1| of this connection is the terminal to be connected to the positive pole of the plate battery 13. Separate grid leaks 15-1] are connected between -the grids 10-3I and cathodes 83-85. The two grid circuits are tuned by the slidable armature members 51-50. Two of the filament leads 81-80 are connected to the tubular members 9|-93, and the other filament leads 95-91 are run within the tubular member. 'I'he filament leads are connected to a suitable source of power '99. The negative terminal of the plate battery 13 may be connected to the lament battery or cathode. In the arrangement shown in Figure III the tubular members 9|-93, connected between the cathodes 83-85, form a tuned cathode circuit. A suitable adjustable conductor |0| may be used to vary the length of the tuned circuit` and hence its resonant frequency. 'I'he tubular members may be eliminated by including a suitable inductance coil within the shield. In the connection shown the grid circuits are tuned by the inductance oi' the shielding member |03 and capacity of the adjustable armatures which are connected to the shield. The shield may be cylindrical or spherical, and fabricated from two or more pieces. The antenna wires are not shown .but may be of a quarter wave length long and connected to points on the shield which offer suitable reactance for the frequency chosen.

'Ihe arrangement shown in Figure IV is not unlike Figure III. The essential difference is found in the circuit which is a push pulloscillator of the .well known Hartley type. In this Figure both the grids 20|-203 and the plates 2,125 cee connected to the shield 233 and the negative terminal of the B battery. Due to the increased capacities of this circuit, the range of oscillation is not as great as found in the circuits of the other figures. In the matter of frequency stability, the single tube Hartley circuit has proven to be the most stable; while the push pull Hartley arrangement is the least stable for variations in plate potential. If an amplifier stage is desired, the amplifier may likewise be included within a metallic shield.

'Ihe circuits described above approach the optimum for the generation of ultra high frequencies. The several illustrations indicate coupling between the oscillator electrodes and sections of the resonant tank circuit near anti-nodal potential points. 'I'he resonant circuit is of relatively low impedance but the tube impedance acts as a load across the anti-nodal potential points and tends to reduce frequency stability. The frequency stability may be greatly improved by coupling the oscillator to that portion of the tank circuit which lies near the equatorial region or adjacent current anti-nodal points of the shield. 'Ihis type of connection places the load where it will minimize the effect on the resonant circuit andthe frequency stability of the oscillatory currents.

In Figure V the shielding member 30| has mounted at its axial poles a pair of screws 303- 305. On the inner ends of the screws are fixed armature members 301-309. The shield forms the inductance and the armatures the capacity of an adjustable resonant circuit. The antinodal current points lie near the equatorial region of the shield. Adjacent these points are mounted condenser plates 3||3|3 which are supportedv with respect to the shield by suitable insulators 3|5, 3|1. 'I'he grid ofthe thermionic tube 3|9 is connected to one condenser plate 3|5 and the plate is connected to the other condenser plate 3|1. A grid leak resistor 32| is connected between grid and the shield. A radio frequency choke 323 is connected between plate and the positive terminal of the B battery 325. 'I'he cathode and one heater lead are connected to the shield. The heater is energized by a battery 321. The circuit arrangement of Figure V is most suitable for the generation of oscillations of substantially constant frequency because the tube load is connected across anti-nodal current points in the resonant circuit.

It should be understood that the precise shape of the shield is not essential. I prefer the spherical, but cylindrical and other shapes may serve equally well. Other obvious modifications within the scope of my invention will occur to those skilled in the art. I do not intend to limit my invention except as required by the prior art and the appended claims.

I claim as my invention: I

l. An oscillatory system comprising a shield, a

adjustable capacity disposed within said shield,

said shield and said capacity forming a resonant tank circuit, an electronic oscillator disposed within said shield, and means coupling said oscillator adjacent an anti-nodal current point within said shield.

2. An oscillatory system comprising a shield, an adjustable capacity disposed within and connected to said shield, said shield and said capacity forming a resonant circuit, a pair of electronic oscillator tubes arranged in push pull connection and disposed within said shield, and

means coupling the input of said oscillator tubes 1I forming an adjustable tank circuit, a thermionic -tube disposed within said shield, means coupling said thermionic tube to said tank circuit, and a pair of oppositely disposed quarter wave length antenna conductors connected to said shield.-

4. In an ultra high frequency system. a shield,

an adiustable capacity substantially centrally disv posed within said shield, said shield forming an u coll.

cuit, a thermionic tube having grid, iilament, and plate electrodes disposed'within said shield, means coupling said grid to one armature of said adjustable capacity, means coupling said plate to the other armature of said adjustablecapacity, said means for coupling the plate and adjustable capacity being of different coupling value from the means coupling the grid and said adjustable capacity, a grid leak resistance connected between gridand shield, a radio frequency choke coil connected to said plate, a source of power disposed external to said shie1d.,and connections from said source to said electrodes and choke 

